1. Field of the Invention
the present invention relates to a control method for a controlling an unmanned vehicle, and more particularly, to control a method designed so that any type of unmanned vehicle, the travel section of which is equipped with wheels, crawlers, etc., can be controlled by commands supplied from control section.
2. Description of the Prior Art
Research concerning the development of self-contained unmanned vehicles (robot cars) is currently being carried out on a very active scale. The existing types of unmanned vehicle are designed so that the travel sections thereof are equipped with wheels, crawlers, etc., and in which the travel motion is accomplished under the control of a control section.
FIG. 7 is a block schematic diagram of the construction of a conventional self-contained unmanned vehicle whose travel section is equipped with wheels. As shown in the figure, item 2 denotes the control section, item 3 the wheel drive section, items 4a and 4b the motors driving the left and right wheels 5a and 5b, respectively, whereby the wheel drive section 3, the motors 4a and 4b, and the wheels 5a and 5b constitute the travel section 6.
If, with this construction, a target location is given, the control section 2 will search the travel path until the target location is reached and use the results of this search to establish the travel commands (hereinafter called commands) and supply the commands to the wheel drive section 3. The wheel drive section 3 will read (decipher) the commands and drive wheels 5a and 5b in accordance with the command.
FIGS. 8(a) and 8(b) show examples of a conventional command (GO command) scheme. If, for example, a set of GO commands consisting of the GO commands 60, 100, 10, 30, 2000 is furnished by the control section 2 to the wheel drive section 3 (FIG. 8(a)), the wheel drive section 3 will read (decipher) the commands to drive the unmanned vehicle as shown in FIG. 8(a). The unmanned vehicle 1 will thus be set in a rectilinear forward motion along the x-axis, start to negotiate a curve at the point corresponding to x=60 cm, and pass the coordinates x=100 cm and y=10 cm in a direction forming an angle of 30.degree. with respect to the x-axis, whereupon it will again travel in a rectilinear forward motion. If, therefore, the new rectilinear forward direction is given as having the new coordinate axis x1, it follows that the new coordinate axis x1 and the old coordinate axis x form an angle of 30.degree. with respect to each other. The travel speed is a constant speed of 2 km (=2000 mm) per hour.
If another set of GO commands consisting of the GO commands 100, 50, 80, 135, and 0 (FIG. 8(b)) is given, the robot car 1 advances in a rectilinear forward motion along the x-axis and proceeds until it reaches the location corresponding to x=100 cm, at which point it will enter a sharp bend and proceed until it reaches the coordinates x=50 cm and y=80 cm and come to a rest at a point forming an angle of 135.degree. with respect to the x-axis. In this instance, the travel speed is slowed down at a constant rate of deceleration so that the vehicular speed will be brought to zero when the point corresponding to x=50 cm and y=80 cm is reached.
By this scheme, the wheel drive section 3 reads (deciphers) the commands furnished by the control section to drive the wheels 5a and 5b. For controlling the wheels 5a and 5b, it is therefore sufficient for the wheel drive section 3 to consider only the local coordinates. Furthermore, the control section 2 searches the travel path and establishes the commands by checking the coordinates of the given universe so that the robot can travel to the destination location.
(Problems the Present Invention Purports to Resolve) However, the conventional type of unmanned vehicle (robot car) described hereinabove has the following shortcomings.
(1) The control section is required to provides very detailed instructions, including such details as the incipient point of entry of a curve and the final point of a curve. Since these point locations will be different according to whether the travel section is equipped with a certain type of locomotive device, such as wheels, crawlers, or mobile legs, it follows that the commands will have to be different in accordance with the nature or shape of the travel section (travel function) so that the program of the control section will be largely dependent upon the nature or shape of the travel section.
To demonstrate the above-noted problem reference is made to in FIG. 9 and FIG. 10. Assume that the travel speed V1 is specified as being a relatively high velocity until the vehicle reaches node N2. If a sudden stop is specified at the next node N3, it may not be possible to fully control the vehicle's inertia, depending on the nature or shape of the travel section, so that deceleration results as shown by the continuous line, even though the vehicle should be decelerated as shown by the dotted line in FIG. 9. As a result, the vehicle will not come to rest until is has overshot the target location of node 3. To prevent such overshooting due to inertial forces, it is necessary, as shown FIG. 10, to specify a relatively lower speed V2 at the moment in which the vehicle has traversed node N1 to compensate for the particular nature or shape of the travel section. This implies, however, that the program of the control section is significantly dependent upon the nature or shape of the travel section. If, furthermore, the vehicle travels at a low speed from node N1 to node N2, the travel time will increase, so that, as a result, the operational productivity will decrease.
(2) When no particular command is given as the vehicle passes through a bend or curve, the vehicle will, therefore, not be able to negotiate the bend or curve along the normal path, due to the particular nature or shape of the travel section, given that the vehicle travels at a constant speed. As a result, the unmanned vehicle will not be capable of smoothly negotiating curves or bends.